The present invention relates to in-ground termite bait stations for containing termite-edible bait material to monitor and/or control termite activity.
Various types of in-ground bait stations have been developed for monitoring and/or controlling termite activity. One known type of station includes a tubular outer housing that is implanted in the ground with an upper end of the housing substantially flush with the ground level. A tubular bait cartridge containing a quantity of bait material (with or without any toxic active ingredient) is inserted into the outer housing. The housing and the cartridge have openings that allow subterranean termites to access the bait material in the cartridge. Known bait stations have included provisions for assuring that the openings in the outer housing and bait cartridge are aligned when the cartridge is installed in the housing. Subterranean termites that discover the bait material in the bait station will build tunnels leading to openings in the outer housing, and will use soil to construct tubes leading from the openings in the outer housing to the aligned openings in the bait cartridge. The termites are then able to access the bait in the cartridge via the tubes.
These tubes are broken when the bait cartridge is removed from the outer housing during periodic checks of the bait station for monitoring the termite activity at the station. After the cartridge is replaced, termites must rebuild the tubes from the outer housing to the bait cartridge before the termites can again begin accessing the bait in the cartridge. The disruption of the tubes tends to disrupt the pheromone trails that termites create to guide other termites to the bait. Until the tubes are rebuilt, termites will tend not to begin feeding on the bait in substantial numbers.
U.S. Pat. No. 5,901,496, incorporated herein by reference, discloses a termite bait station that addresses the above issues by providing a boss around each opening in the bait cartridge. The boss surrounds the opening on all sides and extends radially outward toward the inner surface of the outer housing so as to reduce the radial gap between the cartridge and the housing that must be traversed by termites. To assure proper alignment of the openings in the cartridge and housing, the cartridge has a lead thread or projection that engages a circumferentially extending groove in the outer housing; the cartridge is rotated in a predetermined direction relative to the outer housing until the projection abuts the end of the groove, which establishes the proper aligned relation between the openings.
The present invention improves upon the technology represented by the ""496 patent described above, by providing a bait cartridge configuration that does not rely on or require any particular rotational orientation of the cartridge relative to the outer housing. The outer housing need not be specially adapted to position the cartridge in a particular rotational orientation, and consequently the cartridge can be used with various outer housing configurations. At the same time, the cartridge includes features for reducing the radial gap between the cartridge and housing and for channeling termites into the openings in the cartridge.
In accordance with the invention, a bait cartridge comprises a tubular side wall extending from a lower end to an upper end thereof, a bottom wall joined to the lower end of the tubular side wall to close the lower end, and a plurality of circumferentially elongate apertures formed through the tubular side wall to allow termites to access an interior of the bait cartridge; each aperture has an upper edge, a lower edge, and two opposite end edges. A circumferentially extending upper rib protrudes from the upper edge of each aperture radially outwardly beyond an outer surface of the tubular side wall, and a circumferentially extending lower rib protrudes from the lower edge of each aperture radially outwardly beyond the outer surface of the tubular side wall. The ribs reduce the radial gap that must be traversed by a termite passing from the outer housing to the bait cartridge. The ribs also form circumferentially extending channels for producing a channeling effect tending to lead termites into the apertures in the cartridge. Significantly, the end edges of the apertures are free of any radially outward protrusions so as not to disrupt the channeling effect of the ribs. Thus, regardless of where on the cartridge a termite first makes contact with the cartridge, the termite will tend to be channeled by the ribs into an aperture and thus will be led to the bait. Accordingly, even if the apertures in the cartridge are only partially aligned with the openings in the outer housing, termites will still be channeled to the apertures in the cartridge.
The cartridge preferably has a plurality of longitudinally extending rows of the apertures, the rows being spaced about the circumference of the cartridge. Each row has a plurality of apertures spaced apart along the length of the cartridge. To allow termites to enter the cartridge while preventing larger pests from entering, the apertures preferably have a width of about 2-3 mm.
Preferably the apertures around the circumference collectively take up a majority of the circumference, with relatively narrow spaces between adjacent apertures in the circumferential direction; in this manner, when the outer housing likewise has openings appropriately distributed about its circumference, the apertures will be at least partially aligned with openings in the housing for any rotational orientation of the cartridge. In a preferred embodiment of the invention, each aperture has a circumferential length of about 25 mm and there are four rows of the apertures about the circumference. The cartridge has a diameter of about 35-40 mm. Thus, the apertures collectively have a circumferential extent of about 100 mm, out of a total circumference of about 110 to 125 mm.
The cartridge preferably includes a viewing window in its tubular side wall for monitoring how much bait material remains in the cartridge. The cartridge in a preferred embodiment is constructed of a substantially transparent material, and the window comprises a solid portion of the side wall having no apertures. The solid portion preferably is provided with a smoother surface finish than the rest of the cartridge to enhance its transparency.
In a termite bait device comprising the bait cartridge in combination with a tubular outer housing, the outer housing includes a plurality of openings located so as to be at least partially aligned with apertures in the cartridge when the cartridge is installed in the housing. When the cartridge includes four rows of apertures as described, the housing preferably also includes four rows of openings; the openings in each row are longitudinally spaced at a center-to-center distance corresponding to that of the apertures in the cartridge. Preferably the apertures in the cartridge and the openings in the housing are circumferentially elongate; for example, in one embodiment, the apertures are about 25 mm long and the openings are about 20 mm long in the circumferential direction. The largest circumferential spacing between adjacent openings in the housing preferably is about 25-30 mm, while the largest spacing between adjacent apertures in the cartridge is about 5 mm. Accordingly, in any rotational orientation of the cartridge relative to the housing, the apertures are always at least partially aligned with the openings. The ribs then channel termites into the apertures even if a termite first contacts the cartridge at a location between adjacent apertures.
The outer housing and cartridge preferably have bottom walls that close the lower ends of their tubular side walls. The bottom walls preferably have drainage holes to allow excess moisture to drain from the bait station. The upper end of the cartridge preferably is closed by a removable cap. The cap and cartridge preferably have cooperative locking features that engage each other to retain the cap in place.
The upper end of the housing preferably is closed by a removable cover. The cover and tubular side wall of the housing have cooperative locking features that engage each other to retain the cover in place preventing access to the cartridge. The locking features of the housing preferably are such as to enable the cover to be locked in place by twisting the cover in one direction relative to the housing, and to be unlocked by twisting the cover in the opposite direction. The housing preferably includes an annular flange extending radially outwardly from its upper end, and the cover preferably lies substantially flat against the upper surface of the flange when locked in place. The cover preferably has no projections that can be grasped for twisting it, thereby deterring unwanted access to the interior of the housing by persons or animals. A recess or slot is provided in the cover, into which a tool can be inserted to twist the cover open.